Doc: De-duplicate lists

"\group", "\annotatedlist", and "\generatelist{related}" each produce
a list based on a group. We don't want more than one of those on a given
page.

Task-number: QTBUG-33360
Change-Id: Iebe00f0aa6d49df2aa1715e69629094aef86652e
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>